Insights into the trypanothione system in antimony-resistant and sensitive Leishmania tropica clinical isolates

Pentavalent antimonials are the mainstay treatment against different clinical forms of leishmaniasis. The emergence of resistant isolates in endemic areas has led to treatment failure. Unraveling the underlying resistance mechanism would assist in improving the treatment strategies against resistant isolates. This study aimed to investigate the RNA expression level of glutathione synthetase (GS), Spermidine synthetase (SpS), trypanothione synthetase (TryS) genes involved in trypanothione synthesis, and thiol-dependent reductase (TDR) implicated in drug reduction, in antimony-sensitive and -resistant Leishmania tropica isolates. We investigated 11 antimony-resistant and 11 antimony-sensitive L. tropica clinical isolates from ACL patients. Drug sensitivity of amastigotes was determined in mouse macrophage cell line J774A.1. The RNA expression level in the promastigote forms was analyzed by quantitative real-time PCR. The results revealed a significant increase in the average expression of GS, SpS, and TrpS genes by 2.19, 1.56, and 2.33-fold in resistant isolates compared to sensitive ones. The average expression of TDR was 1.24-fold higher in resistant isolates, which was insignificant. The highest correlation coefficient between inhibitory concentration (IC50) values and gene expression belonged to the TryS, GS, SpS, and TDR genes. Moreover, the intracellular thiol content was increased 2.17-fold in resistant isolates compared to sensitive ones and positively correlated with IC50 values. Our findings suggest that overexpression of trypanothione biosynthesis genes and increased thiol content might play a key role in the antimony resistance of L. tropica clinical isolates. In addition, the diversity of gene expression in the trypanothione system and thiol content among L. tropica clinical isolates highlighted the phenotypic heterogeneity of antimony resistance among the parasite population.

Targeting Trypanothione Metabolism in Trypanosomatids

Infectious diseases caused by trypanosomatids, including African trypanosomiasis (sleeping sickness), Chagas disease, and different forms of leishmaniasis, are Neglected Tropical Diseases affecting millions of people worldwide, mainly in vulnerable territories of tropical and subtropical areas. In general, current treatments against these diseases are old-fashioned, showing adverse effects and loss of efficacy due to misuse or overuse, thus leading to the emergence of resistance. For these reasons, searching for new antitrypanosomatid drugs has become an urgent necessity, and different metabolic pathways have been studied as potential drug targets against these parasites. Considering that trypanosomatids possess a unique redox pathway based on the trypanothione molecule absent in the mammalian host, the key enzymes involved in trypanothione metabolism, trypanothione reductase and trypanothione synthetase, have been studied in detail as druggable targets. In this review, we summarize some of the recent findings on the molecules inhibiting these two essential enzymes for Trypanosoma and Leishmania viability.

Functional identification of bacterial spermine, thermospermine, norspermine, norspermidine, spermidine, and N1-aminopropylagmatine synthases

Spermine synthase is an aminopropyltransferase that adds an aminopropyl group to the essential polyamine spermidine to form tetraamine spermine, needed for normal human neural development, plant salt and drought resistance, and yeast CoA biosynthesis. We functionally identify for the first time bacterial spermine synthases, derived from phyla Bacillota, Rhodothermota, Thermodesulfobacteriota, Nitrospirota, Deinococcota, and Pseudomonadota. We also identify bacterial aminopropyltransferases that synthesize the spermine same mass isomer thermospermine, from phyla Cyanobacteriota, Thermodesulfobacteriota, Nitrospirota, Dictyoglomota, Armatimonadota, and Pseudomonadota, including the human opportunistic pathogen Pseudomonas aeruginosa. Most of these bacterial synthases were capable of synthesizing spermine or thermospermine from the diamine putrescine and so possess also spermidine synthase activity. We found that most thermospermine synthases could synthesize tetraamine norspermine from triamine norspermidine, that is, they are potential norspermine synthases. This finding could explain the enigmatic source of norspermine in bacteria. Some of the thermospermine synthases could synthesize norspermidine from diamine 1,3-diaminopropane, demonstrating that they are potential norspermidine synthases. Of 18 bacterial spermidine synthases identified, 17 were able to aminopropylate agmatine to form N1-aminopropylagmatine, including the spermidine synthase of Bacillus subtilis, a species known to be devoid of putrescine. This suggests that the N1-aminopropylagmatine pathway for spermidine biosynthesis, which bypasses putrescine, may be far more widespread than realized and may be the default pathway for spermidine biosynthesis in species encoding L-arginine decarboxylase for agmatine production. Some thermospermine synthases were able to aminopropylate N1-aminopropylagmatine to form N12-guanidinothermospermine. Our study reveals an unsuspected diversification of bacterial polyamine biosynthesis and suggests a more prominent role for agmatine.

Overexpression and biochemical characterization of a carboxyspermidine dehydrogenase from Agrobacterium fabrum str. C58 and its application to carboxyspermidine production

BACKGROUND

Carboxyspermidine (C-Spd) is a potentially valuable polyamine carboxylate compound and an excellent building block for spermidine synthesis, which is a critical polyamine with significant implications for human health and longevity. C-Spd can also be used to prepare multivalent cationic lipids and modify nucleoside probes. Because of these positive effects on human health, C-Spd is of considerable interest as a food additive and pharmaceutical target.

RESULTS

A putative gene afcasdh from Agrobacterium fabrum str. C58, encoding carboxyspermidine dehydrogenase with C-Spd biosynthesis activity, was synthesized and transformed into Escherichia coli BL21 (DE3) for overexpression. The recombinant AfCASDH was purified and fully characterized. The optimum temperature and pH for the recombinant enzyme were 30 °C and 7.5, respectively. The coupled catalytic strategy of AfCASDH and various NADPH regeneration systems were developed to enhance the efficient production of C-Spd compound. Finally, the maximum titer of C-Spd production successfully achieved 1.82 mmol L^-1 with a yield of 91% by optimizing the catalytic conditions.

CONCLUSION

A novel AfCASDH from A. fabrum str. C58 was characterized that could catalyze the formation of C-Spd from putrescine and l-aspartate-β-semialdehyde (L-Asa). A whole-cell catalytic strategy coupled with NADPH regeneration was established successfully for C-Spd biosynthesis for the first time. The coupled system indicated that AfCASDH might provide a feasible method for the industrial production of C-Spd. © 2021 Society of Chemical Industry.

Trypanothione Metabolism as Drug Target for Trypanosomatids

Chagas Disease, African sleeping sickness, and leishmaniasis are neglected diseases caused by pathogenic trypanosomatid parasites, which have a considerable impact on morbidity and mortality in poor countries. The available drugs used as treatment have high toxicity, limited access, and can cause parasite drug resistance. Long-term treatments, added to their high toxicity, result in patients that give up therapy. Trypanosomatids presents a unique trypanothione based redox system, which is responsible for maintaining the redox balance. Therefore, inhibition of these essential and exclusive parasite's metabolic pathways, absent from the mammalian host, could lead to the development of more efficient and safe drugs. The system contains different redox cascades, where trypanothione and tryparedoxins play together a central role in transferring reduced power to different enzymes, such as 2-Cys peroxiredoxins, non-selenium glutathione peroxidases, ascorbate peroxidases, glutaredoxins and methionine sulfoxide reductases, through NADPH as a source of electrons. There is sufficient evidence that this complex system is essential for parasite survival and infection. In this review, we explore what is known in terms of essentiality, kinetic and structural data, and the development of inhibitors of enzymes from this trypanothione-based redox system. The recent advances and limitations in the development of lead inhibitory compounds targeting these enzymes have been discussed. The combination of molecular biology, bioinformatics, genomics, and structural biology is fundamental since the knowledge of unique features of the trypanothione-dependent system will provide tools for rational drug design in order to develop better treatments for these diseases.

Examination of a first-in-class bis-dialkylnorspermidine-terphenyl antibiotic in topical formulation against mono and polymicrobial biofilms

Biofilm-impaired tissue is a significant factor in chronic wounds such as diabetic foot ulcers. Most, if not all, anti-biotics in clinical use have been optimized against planktonic phenotypes. In this study, an in vitro assessment was performed to determine the potential efficacy of a first-in-class series of antibiofilm antibiotics and compare outcomes to current clinical standards of care. The agent, CZ-01179, was formulated into a hydrogel and tested against mature biofilms of a clinical isolate of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa ATCC 27853 using two separate methods. In the first method, biofilms were grown on cellulose discs on an agar surface. Topical agents were spread on gauze and placed over the biofilms for 24 h. Biofilms were quantified and imaged with confocal and scanning electron microscopy. In the second method, biofilms were grown on bioabsorbable collagen coupons in a modified CDC biofilm reactor. Coupons were immersed in treatment for 24 h. The first method was limited in its ability to assess efficacy. Efficacy profiles against biofilms grown on collagen were more definitive, with CZ-01179 gel eradicating well-established biofilms to a greater degree compared to clinical standards. In conclusion, CZ-01179 may be a promising topical agent that targets the biofilm phenotype. Pre-clinical work is currently being performed to determine the translatable potential of CZ-01179 gel.

Rice phenolamindes reduce the survival of female adults of the white-backed planthopper Sogatella furcifera

In response to infestation by herbivores, rice plants rapidly biosynthesize defense compounds by activating a series of defense-related pathways. However, which defensive compounds in rice are effective against herbivores remains largely unknown. We found that the infestation of white-backed planthopper (WBPH) Sogatella furcifera gravid females significantly increased levels of jasmonic acid (JA), jasmonoyl-isoleucine (JA-Ile) and H2O2, and reduced the level of ethylene in rice; levels of 11 of the tested 12 phenolamides (PAs) were subsequently enhanced. In contrast, WBPH nymph infestation had no effect on levels of JA, JA-Ile, ethylene and H2O2 in rice, and enhanced levels of only 2 of 12 PAs. Moreover, infestation by brown planthopper Nilaparvata lugens gravid females also affected the production of these PAs differently. Bioassays revealed that 4 PAs - N-feruloylputrescine, N-feruloyltyramine, feruloylagmatine and N1,N10-diferuloylspermidine - were toxic to newly emerged WBPH female adults. Our results suggest that WBPH- or BPH-induced biosynthesis of PAs in rice seems to be shaped primarily by the specific profile of defense-related signals elicited by the herbivore and that PAs play a role in conferring the resistance to WBPH on rice.

Separation and Characterization of Phenolamines and Flavonoids from Rape Bee Pollen, and Comparison of Their Antioxidant Activities and Protective Effects Against Oxidative Stress

Phenolamines and flavonoids are two important components in bee pollen. There are many reports on the bioactivity of flavonoids in bee pollen, but few on phenolamines. This study aims to separate and characterize the flavonoids and phenolamines from rape bee pollen, and compare their antioxidant activities and protective effects against oxidative stress. The rape bee pollen was separated to obtain 35% and 50% fractions, which were characterized by HPLC-ESI-QTOF-MS/MS. The results showed that the compounds in 35% fraction were quercetin and kaempferol glycosides, while the compounds in 50% fraction were phenolamines, including di-p-coumaroyl spermidine, p-coumaroyl caffeoyl hydroxyferuloyl spermine, di-p-coumaroyl hydroxyferuloyl spermine, and tri-p-coumaroyl spermidine. The antioxidant activities of phenolamines and flavonoids were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), and ferric reducing antioxidant power (FRAP) assays. It was found that the antioxidant activity of phenolamines was significantly higher than that of flavonoids. Moreover, phenolamines showed better protective effects than flavonoids on HepG2 cells injured by AAPH. Furthermore, phenolamines could significantly reduce the reactive oxygen species (ROS), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, and increase the superoxide dismutase (SOD) and glutathione (GSH) levels. This study lays a foundation for the further understanding of phenolamines in rape bee pollen.

Specific effects of antitumor active norspermidine on the structure and function of DNA

We compared the effects of trivalent polyamines, spermidine (SPD) and norspermidine (NSPD), a chemical homologue of SPD, on the structure of DNA and gene expression. The chemical structures of SPD and NSPD are different only with the number of methylene groups between amine groups, [N-3-N-4-N] and [N-3-N-3-N], respectively. SPD plays vital roles in cell function and survival, including in mammals. On the other hand, NSPD has antitumor activity and is found in some species of plants, bacteria and algae, but not in humans. We found that both polyamines exhibit biphasic effect; enhancement and inhibition on in vitro gene expression, where SPD shows definitely higher potency in enhancement but NSPD causes stronger inhibition. Based on the results of AFM (atomic force microscopy) observations together with single DNA measurements with fluorescence microscopy, it becomes clear that SPD tends to align DNA orientation, whereas NSPD induces shrinkage with a greater potency. The measurement of binding equilibrium by NMR indicates that NSPD shows 4-5 times higher affinity to DNA than SPD. Our theoretical study with Monte Carlo simulation provides the insights into the underlying mechanism of the specific effect of NSPD on DNA.

Structure and Function of the Acetylpolyamine Amidohydrolase from the Deep Earth Halophile Marinobacter subterrani

Polyamines are small organic cations that are essential for cellular function in all kingdoms of life. Polyamine metabolism is regulated by enzyme-catalyzed acetylation-deacetylation cycles in a fashion similar to the epigenetic regulation of histone function in eukaryotes. Bacterial polyamine deacetylases are particularly intriguing, because these enzymes share the fold and function of eukaryotic histone deacetylases. Recently, acetylpolyamine amidohydrolase from the deep earth halophile Marinobacter subterrani (msAPAH) was described. This Zn2+-dependent deacetylase shares 53% amino acid sequence identity with the acetylpolyamine amidohydrolase from Mycoplana ramosa (mrAPAH) and 22% amino acid sequence identity with the catalytic domain of histone deacetylase 10 from Danio rerio (zebrafish; zHDAC10), the eukaryotic polyamine deacetylase. The X-ray crystal structure of msAPAH, determined in complexes with seven different inhibitors as well as the acetate coproduct, shows how the chemical strategy of Zn2+-dependent amide hydrolysis and the catalytic specificity for cationic polyamine substrates is conserved in a subterranean halophile. Structural comparisons with mrAPAH reveal that an array of aspartate and glutamate residues unique to msAPAH enable the binding of one or more Mg2+ ions in the active site and elsewhere on the protein surface. Notwithstanding these differences, activity assays with a panel of acetylpolyamine and acetyllysine substrates confirm that msAPAH is a broad-specificity polyamine deacetylase, much like mrAPAH. The broad substrate specificity contrasts with the narrow substrate specificity of zHDAC10, which is highly specific for N8-acetylspermidine hydrolysis. Notably, quaternary structural features govern the substrate specificity of msAPAH and mrAPAH, whereas tertiary structural features govern the substrate specificity of zHDAC10.

In vitro testing of a first-in-class tri-alkylnorspermidine-biaryl antibiotic in an anti-biofilm silicone coating

Biofilm-related infection is among the worst complication to prosthetic joint replacement procedures; once established on the implant surface, biofilms show strong recalcitrance to clinical antibiotic therapy, frequently requiring costly revision procedures and prolonged systemic antibiotics for their removal. A well-designed active release coating might assist host immunity in clearing bacterial contaminants within the narrow perioperative window and ultimately prevent microbial colonization of the joint prosthesis. A first-in-class compound (CZ-01127) was tested as the active release agent in a silicone (Si) coating using an in vitro dynamic flow model of surgical site contamination and compared with analogous coatings containing clinical gold-standard antibiotics vancomycin and gentamicin; the CZ-01127 coating outperformed both vancomycin and gentamicin coatings and was the only to decrease the methicillin-resistant Staphylococcus aureus (MRSA) inocula below detectable limits for the first 3 days. The antimicrobial activity of CZ-01127, and for comparison vancomycin and gentamicin, were characterized against both planktonic and biofilm MRSA using the minimum inhibitory concentration (MIC) assay, serial passages, and serial dilution tests against established biofilms grown with a CBR 90 CDC biofilm reactor. Despite a similar MIC (1 µg/ml) and behavior in a 25-day serial passage analysis, CZ-01127 displayed much greater bactericidal activity against established biofilms and was the only to decrease biofilm colony forming units (CFUs) below detectable limits at the highest concentration tested (500 µg/ml). Coating release profiles were characterized using ATR-FTIR and displayed burst release kinetics within the decisive period of the perioperative window suggesting the silicon carrier is broadly useful for screening antibiotic compound for local delivery applications. STATEMENT OF SIGNIFICANCE: With an aging population, an increasing number of people are undergoing total joint replacement procedures in which diseased joint tissues are replaced with permanent metallic implants. Some of these procedures are burdened by costly and debilitating infections. A promising approach to prevent infections is the use of an antimicrobial coating on the surface of the implant which releases antibiotics into the surgical site to prevent infection. In this study, we tested a new antibiotic compound formulated in a silicone coating. Data showed that this compound was more effective at killing pathogenic methicillin resistant Staphylococcus aureus (MRSA) bacteria than two clinical gold-standard antibiotics-vancomycin and gentamicin-and could be a promising agent for antimicrobial coating technologies.

In vivo analysis of a first-in-class tri-alkyl norspermidine-biaryl antibiotic in an active release coating to reduce the risk of implant-related infection

Prosthetic joint infection (PJI) is a well-known and persisting problem. Active release coatings have promise to provide early protection to an implant by eradicating small colony biofilm contaminants or planktonic bacteria that can form biofilm. Traditional antibiotics can be limited as active release agents in that they have limited effect against biofilms and develop resistance at sub-lethal concentrations. A unique first-in-class compound (CZ-01127) was assessed as the active release agent in a silicone (Si)-based coating to prevent PJI in a sheep model of joint space infection. Titanium (Ti) plugs contained a porous coated Ti (PCTi) region and polymer-coated region. Plugs were implanted into a femoral condyle of sheep to assess the effect of the Si polymer on cancellous bone ingrowth, the effect of CZ-01127 on bone ingrowth, and the ability of CZ-01127 to prevent PJI. Microbiological results showed that CZ-01127 was able to eradicate bacteria in the local region of the implanted plugs. Data further showed that Si did not adversely affect bone ingrowth. However, bacteria that reached the joint space (synovium) were not fully eradicated. Outcomes suggested that the CZ-01127 coating provided local protection to the implant system in a challenging model, the design of which could be beneficial for testing future antimicrobial therapies for PJI. STATEMENT OF SIGNIFICANCE: Periprosthetic joint infection (PJI) is now commonplace, and constitutes an underlying problem that patients and physicians face. Active release antibiotic coatings have potential to prevent these infections. Traditional antibiotics are limited in their ability to eradicate bacteria that reside in biofilms, and are more susceptible to resistance development. This study addressed these limitations by testing the efficacy of a unique antimicrobial compound in a coating that was tested in a challenging sheep model of PJI. The unique coating was able to eradicate bacteria and prevent infection in the environment adjacent to the implant. Bacteria that escaped into the joint space still caused infection, yet benchmark data can be used to optimize the coating and translate it toward clinical use.

Serum polyamine metabolic profile in autoimmune thyroid disease patients

OBJECTIVE

Polyamines are indispensable polycations and play important physiological roles in living cells. Some polyamine metabolites have been associated with autoimmune disorders. The aims of this study were to profile polyamine metabolites in autoimmune thyroid disease (AITD) and predict whether polyamine metabolites are associated with thyroid hormone, thyroid autoantibodies or disease progression.

DESIGN, PATIENTS AND MEASUREMENTS

A total of 136 participants were recruited, including Graves' disease (GD) (n = 36), Hashimoto's thyroiditis (HT) (n = 33) and thyroid autoantibody-positive (pTAb) (n = 29) patients and 38 age- and sex-matched healthy controls (HCs). Fourteen polyamine metabolites, including polyamine precursors, polyamines and polyamine catabolite, were measured by UFLC-MS/MS RESULTS: Both GD and HT patients had higher L-arginine, L-ornithine, lysine and agmatine levels and lower putrescine, 1,3-diaminopropane, spermine, N-acetylputrescine levels than HCs. Some polyamine metabolite levels were different only in GD or HT patients compared to HCs: GD patients had significantly higher spermidine, N-acetylspermidine and γ-aminobutyric acid and lower cadaverine, whereas HT patients had significantly decreased N-acetylspermine. Only spermine and N-acetylspermine were significantly lower in pTAb than HCs. The spermine:spermidine ratio was significantly reduced in all AITD patients. In addition, spermine was negatively correlated with thyroid-specific antibodies grade. N-acetylspermidine might be a risk factor for pTAb progression to overt hypothyroidism.

CONCLUSIONS

Compared with the HCs, most metabolites of GD and HT showed similar patterns, suggesting the possibility of a common pathophysiological basis or metabolic pathway. Moreover, pTAb progression to overt hypothyroidism may be related to high N-acetylspermidine. Thyroid autoimmunity was associated with low spermine.

Ecological Insights to Track Cytotoxic Compounds among Maytenus ilicifolia Living Individuals and Clones of an Ex Situ Collection

Biodiversity is key for maintenance of life and source of richness. Nevertheless, concepts such as phenotype expression are also pivotal to understand how chemical diversity varies in a living organism. Sesquiterpene pyridine alkaloids (SPAs) and quinonemethide triterpenes (QMTs) accumulate in root bark of Celastraceae plants. However, despite their known bioactive traits, there is still a lack of evidence regarding their ecological functions. Our present contribution combines analytical tools to study clones and individuals of Maytenus ilicifolia (Celastraceae) kept alive in an ex situ collection and determine whether or not these two major biosynthetic pathways could be switched on simultaneously. The relative concentration of the QMTs maytenin (1) and pristimerin (2), and the SPA aquifoliunin E1 (3) were tracked in raw extracts by HPLC-DAD and ¹H-NMR. Hierarchical Clustering Analysis (HCA) was used to group individuals according their ability to accumulate these metabolites. Semi-quantitative analysis showed an extensive occurrence of QMT in most individuals, whereas SPA was only detected in minor abundance in five samples. Contrary to QMTs, SPAs did not accumulate extensively, contradicting the hypothesis of two different biosynthetic pathways operating simultaneously. Moreover, the production of QMT varied significantly among samples of the same ex situ collection, suggesting that the terpene contents in root bark extracts were not dependent on abiotic effects. HCA results showed that QMT occurrence was high regardless of the plant age. This data disproves the hypothesis that QMT biosynthesis was age-dependent. Furthermore, clustering analysis did not group clones nor same-age samples together, which might reinforce the hypothesis over gene regulation of the biosynthesis pathways. Indeed, plants from the ex situ collection produced bioactive compounds in a singular manner, which postulates that rhizosphere environment could offer ecological triggers for phenotypical plasticity.

Base excision repair plays an important role in the protection against nitric oxide- and in vivo-induced DNA damage in Trypanosoma brucei

Uracil-DNA glycosylase (UNG) initiates the base excision repair pathway by excising uracil from DNA. We have previously shown that Trypanosoma brucei cells defective in UNG exhibit reduced infectivity thus demonstrating the relevance of this glycosylase for survival within the mammalian host. In the early steps of the immune response, nitric oxide (NO) is released by phagocytes, which in combination with oxygen radicals produce reactive nitrogen species (RNS). These species can react with DNA generating strand breaks and base modifications including deaminations. Since deaminated cytosines are the main substrate for UNG, we hypothesized that the glycosylase might confer protection towards nitrosative stress. Our work establishes the occurrence of genotoxic damage in Trypanosoma brucei upon exposure to NO in vitro and shows that deficient base excision repair results in increased levels of damage in DNA and a hypermutator phenotype. We also evaluate the incidence of DNA damage during infection in vivo and show that parasites recovered from mice exhibit higher levels of DNA strand breaks, base deamination and repair foci compared to cells cultured in vitro. Notably, the absence of UNG leads to reduced infectivity and enhanced DNA damage also in animal infections. By analysing mRNA and protein levels, we found that surviving UNG-KO trypanosomes highly express tryparedoxin peroxidase involved in trypanothione/tryparedoxin metabolism. These observations suggest that the immune response developed by the host enhances the activation of genes required to counteract oxidative stress and emphasize the importance of DNA repair pathways in the protection to genotoxic and oxidative stress in trypanosomes.

Controlling the regioselectivity and stereospecificity of FAD-dependent polyamine oxidases with the use of amine-attached guide molecules as conformational modulators

Enzymes generally display strict stereospecificity and regioselectivity for their substrates. Here by using FAD-dependent human acetylpolyamine oxidase (APAO), human spermine (Spm) oxidase (SMOX) and yeast polyamine oxidase (Fms1), we demonstrate that these fundamental properties of the enzymes may be regulated using simple guide molecules, being either covalently attached to polyamines or used as a supplement to the substrate mixtures. APAO, which naturally metabolizes achiral N1-acetylated polyamines, displays aldehyde-controllable stereospecificity with chiral 1-methylated polyamines, like (R)- and (S)-1-methylspermidine (1,8-diamino-5-azanonane) (1-MeSpd). Among the novel N1-acyl derivatives of MeSpd, isonicotinic acid (P4) or benzoic acid (Bz) with (R)-MeSpd had Km of 3.6 ± 0.6/1.2 ± 0.7 µM and kcat of 5.2 ± 0.6/4.6 ± 0.7 s-1 respectively, while N1 -AcSpd had Km 8.2 ± 0.4 µM and kcat 2.7 ± 0.0 s-1 On the contrary, corresponding (S)-MeSpd amides were practically inactive (kcat < 0.03 s-1) but they retained micromole level Km for APAO. SMOX did not metabolize any of the tested compounds (kcat < 0.05 s-1) that acted as non-competitive inhibitors having Ki ≥ 155 µM for SMOX. In addition, we tested (R,R)-1,12-bis-methylspermine (2,13-diamino-5,10-diazatetradecane) (R,R)-(Me2Spm) and (S,S)-Me2Spm as substrates for Fms1. Fms1 preferred (S,S)- to (R,R)-diastereoisomer, but with notably lower kcat in comparison with spermine. Interestingly, Fms1 was prone to aldehyde supplementation in its regioselectivity, i.e. the cleavage site of spermidine. Thus, aldehyde supplementation to generate aldimines or N-terminal substituents in polyamines, i.e. attachment of guide molecule, generates novel ligands with altered charge distribution changing the binding and catalytic properties with polyamine oxidases. This provides means for exploiting hidden capabilities of polyamine oxidases for controlling their regioselectivity and stereospecificity.

Sphingomonas tabacisoli sp. nov., a member of the genus Sphingomonas, isolated from rhizosphere soil of Nicotiana tabacum L

A Gram-staining-negative, aerobic, motile and rod-shaped bacterium, designated strain X1-8T, was isolated from rhizosphere soil of Nicotiana tabacum L. collected from the tobacco produce base located in Kunming, south-west PR China. Cells showed oxidase-negative and catalase-positive reactions and were motile by means of peritrichous flagella. Growth occurred at 25-40 °C and pH 6.0-8.0 with optimal growth at 30-35 °C, pH 7.0. The major respiratory lipoquinone was Q-10. C16 : 0 and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) were identified as major cellular fatty acids. The profile of polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, sphingoglycolipid, phosphatidylcholine and one unidentified glycolipid. The major polyamine was sym-homospermidine. The genomic DNA G+C content was 66.5 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that X1-8T should be affiliated to the genus Sphingomonasand formed a clade with most closely related species Sphingomonas changbaiensisNBRC 104936T. The results of 16S rRNA gene sequences similarity analysis indicated that X1-8T had the highest similarity with S. changbaiensisNBRC 104936T (98.4 %) and lower than 96.0 % with other species of the genus Sphingomonas. DNA-DNA hybridization data indicated that X1-8T represented a novel genomic species of the genus Sphingomonas. The characteristics determined in the polyphasic taxonomic study indicated that X1-8T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas tabacisoli sp. nov. (type strain X1-8T=KCTC 62032T=CGMCC 1.16275T) is proposed.

Isothermal Self-Assembly of Spermidine-DNA Nanostructure Complex as a Functional Platform for Cancer Therapy

Programmable DNA nanostructure self-assembly offers great potentials in nanomedicine, drug delivery, biosensing, and bioimaging. However, due to the intrinsically negatively charged DNA backbones, the instability of DNA nanostructures in physiological settings poses serious challenges to their practical applications. To overcome this challenge, a strategy that combines the magnesium-free DNA self-assembly and functionalization is proposed in this study. We hypothesize that naturally abundant spermidine may not only mediate the self-assembly of DNA nanostructures, but also shield them from harsh physiological environments. As a proof of concept, a DNA nanoprism is designed and synthesized successfully through spermidine. It is found that spermidine can mediate the isothermal self-assembly of DNA nanoprisms. Compared to conventional Mg²⁺-assembled DNA nanostructures, the spermidine-DNA nanoprism complex shows higher thermal stability and better enzymatic resistance than Mg²⁺-assembled DNA nanoprisms, and more importantly, it has a much higher cellular uptake efficacy in multiple cancerous cell lines. The internalization mechanism is identified as clathrin-mediated endocytosis. To demonstrate the suitability of this new nanomaterial for biomedical applications, an mTOR siRNA, after being conjugated into the complex, is efficiently delivered into cancer cells and shows excellent gene knockdown efficacy and anticancer capability. These findings indicate that the spermidine-DNA complex nanomaterials might be a promising platform for biomedical applications in the future.

Relative contributions of norspermidine synthesis and signaling pathways to the regulation of Vibrio cholerae biofilm formation

The polyamine norspermidine is one of the major polyamines synthesized by Vibrionales and has also been found in various aquatic organisms. Norspermidine is among the environmental signals that positively regulate Vibrio cholerae biofilm formation. The NspS/MbaA signaling complex detects extracellular norspermidine and mediates the response to this polyamine. Norspermidine binding to the NspS periplasmic binding protein is thought to inhibit the phosphodiesterase activity of MbaA, increasing levels of the biofilm-promoting second messenger cyclic diguanylate monophosphate, thus enhancing biofilm formation. V. cholerae can also synthesize norspermidine using the enzyme NspC as well as import it from the environment. Deletion of the nspC gene was shown to reduce accumulation of bacteria in biofilms, leading to the conclusion that intracellular norspermidine is also a positive regulator of biofilm formation. Because V. cholerae uses norspermidine to synthesize the siderophore vibriobactin it is possible that intracellular norspermidine is required to obtain sufficient amounts of iron, which is also necessary for robust biofilm formation. The objective of this study was to assess the relative contributions of intracellular and extracellular norspermidine to the regulation of biofilm formation in V. cholerae. We show the biofilm defect of norspermidine synthesis mutants does not result from an inability to produce vibriobactin as vibriobactin synthesis mutants do not have diminished biofilm forming abilities. Furthermore, our work shows that extracellular, but not intracellular norspermidine, is mainly responsible for promoting biofilm formation. We establish that the NspS/MbaA signaling complex is the dominant mediator of biofilm formation in response to extracellular norspermidine, rather than norspermidine synthesized by NspC or imported into the cell.

Olivibacter composti sp. nov., isolated from compost collected at a greenhouse

A polyphasic approach was used to characterize a presumably novel bacterium, designated strain CC-KYC063T, isolated from a compost sample collected at a greenhouse facility within Taiwan. Strain CC-KYC063T was Gram-stain-negative and aerobic, able to grow at 15-37 °C (optimal 30 °C), at pH 7.0-9.0 (optimal pH 7.0) and with 0-2 % (w/v) NaCl. The 16S rRNA gene sequence of strain CC-KYC063T showed highest similarity to Olivibacter ginsengisoli Gsoil 060T (96.2 %) and Olivibacter terrae Jip13T (95.5 %). The DNA G+C content was 43.0 mol% and the predominant quinone system was menaquinone-7 (MK-7). The polyamine pattern showed a predominance of sym-homospermidine. The major fatty acids found in strain CC-KYC063T were iso-C15 : 0, iso-C17 : 0 3-OH and C16 : 1ω6c/C16 : 1ω7c. Based on the distinct phylogenetic, phenotypic and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence analysis, strain CC-KYC063T is considered to represent a novel species of the genus Olivibacter, for which the name Olivibacter composti sp. nov. is proposed. The type strain is CC-KYC063T (=BCRC 80939T=JCM 31198T).

Chelatococcus reniformis sp. nov., isolated from a glacier

A Gram-stain-negative, non-motile, reniform bacterial strain, B2974T, was isolated from an ice core of the Muztagh Glacier, on the Tibetan Plateau, China. Strain B2974T grew optimally at pH 7.0-7.5 and 25-30 °C in the presence of 0-2.0 % (w/v) NaCl. 16S rRNA gene sequence similarity analysis indicated that strain B2974T was closely related to Chelatococcus asaccharovorans LMG 25503T at a level of 97.1 %. The major quinone of strain B2974T was ubiquinone Q10. The predominant fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C19 : 0 cyclo ω8c. sym-Homospermidine was the major polyamine. The genomic DNA G+C content of the strain was 64 mol%. In DNA-DNA hybridization tests, strain B2974T shared 49.32 % DNA-DNA relatedness with the type strain of Chelatococcus asaccharovorans LMG 25503T. Based on the results of phenotypic and chemotaxonomic characteristics, strain B2974T was considered as a novel species of the genus Chelatococcus, for which the name Chelatococcus reniformis sp. nov. is proposed. The type strain is B2974T (=JCM 30308T=CGMCC 1.12919T).

Effect of Spermidine Analogues on Cell Growth of Escherichia coli Polyamine Requiring Mutant MA261

The effects of spermidine analogues [norspermidine (NSPD, 33), spermidine (SPD, 34), homospermidine (HSPD, 44) and aminopropylcadaverine (APCAD, 35)] on cell growth were studied using Escherichia coli polyamine-requiring mutant MA261. Cell growth was compared at 32°C, 37°C, and 42°C. All four analogues were taken up mainly by the PotABCD spermidine-preferential uptake system. The degree of stimulation of cell growth at 32°C and 37°C was NSPD ≥ SPD ≥ HSPD > APCAD, and SPD ≥ HSPD ≥ NSPD > APCAD, respectively. However, at 42°C, it was HSPD » SPD > NSPD > APCAD. One reason for this is HSPD was taken up effectively compared with other triamines. In addition, since natural polyamines (triamines and teteraamines) interact mainly with RNA, and the structure of RNA is more flexible at higher temperatures, HSPD probably stabilized RNA more tightly at 42°C. We have thus far found that 20 kinds of protein syntheses are stimulated by polyamines at the translational level. Among them, synthesis of OppA, RpoE and StpA was more strongly stimulated by HSPD at 42°C than at 37°C. Stabilization of the initiation region of oppA and rpoE mRNA was tighter by HSPD at 42°C than 37°C determined by circular dichroism (CD). The degree of polyamine stimulation of OppA, RpoE and StpA synthesis by NSPD, SPD and APCAD was smaller than that by HSPD at 42°C. Thus, the degree of stimulation of cell growth by spermidine analogues at the different temperatures is dependent on the stimulation of protein synthesis by some components of the polyamine modulon.

Effects of norspermidine on Pseudomonas aeruginosa biofilm formation and eradication

Biofilms are defined as aggregation of single cell microorganisms and associated with over 80% of all the microbial infections. Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen capable of leading to various infections in immunocompromised people. Recent studies showed that norspermidine, a kind of polyamine, prevented and disrupted biofilm formation by some Gram-negative bacterium. In this study, the effects of norspermidine on P. aeruginosa biofilm formation and eradication were tested. Microtiter plate combined with crystal violet staining was used to study the effects of norspermidine on P. aeruginosa initial attachment, then we employed SEM (scanning electron microscope), qRT-PCR, and QS-related virulence factor assays to investigate how norspermidine prevent biofilm formation by P. aeruginosa. We reported that high-dose norspermidine had bactericide effect on P. aeruginosa, and norspermidine began to inhibit biofilm formation and eradicate 24-h mature biofilm at concentration of 0.1 and 1 mmol/L, respectively, probably by preventing cell-surface attachment, inhibiting swimming motility, and downregulating QS-related genes expression. To investigate the potential utility of norspermidine in preventing device-related infections, we found that catheters immersed with norspermidine were effective in eradicating mature biofilm. These results suggest that norspermidine could be a potent antibiofilm agent for formulating strategies against P. aeruginosa biofilm.

Ammoniphilus resinae sp. nov., an endospore-forming bacterium isolated from resin fragments

A polyphasic approach was used to characterize an endospore-forming bacterium, designated strain CC-RT-ET, isolated from resin fragments. Strain CC-RT-ET was Gram-stain-variable and facultatively anaerobic, able to grow at 20-37 °C (optimal 30 °C) and pH6.0-9.0 (optimal pH 7.0). Ellipsoidal and terminal endospores were observed. The 16S rRNA gene sequence analysis of strain CC-RT-ET showed highest sequence similarity to Ammoniphilus oxalivorans RAOx-FST (97.8 %) and Ammoniphilus oxalaticus RAOx-1T (97.7 %). According to the DNA-DNA hybridization, the relatedness values of strain CC-RT-ET with Ammoniphilus oxalivorans RAOx-FST and Ammoniphilus oxalaticus RAOx-1T were 21 % and 29 %, respectively. The DNA G+C content was 39.2 mol% and the predominant quinone system was menaquinone-7 (MK-7). The major polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylmethylethanolamine. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The polyamine pattern showed predominance of sym-homospermidine and putrescine. The major fatty acids found in strain CC-RT-ET were C14 : 0, iso-C15 : 0, anteiso-C15 : 0 and C16 : 1ω7c/C16 : 1ω6c. Based on the distinct phylogenetic, phenotypic and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence analysis, strain CC-RT-ET is considered to represent a novel species of the genus Ammoniphilus, for which the name Ammoniphilus resinaesp. nov. is proposed. The type strain is CC-RT-ET (=BCRC 80314T=DSM 24738T).

[Enantioselective Synthesis of (R)- and (S)-3-Methylspermidines]

Earlier unknown enantiomerically pure (R)- and (S)-1,8-diamino-3-methyl-4-azaoctane's (3-MeSpd's) were synthesized with high overall yields and optical purity starting from commercially available R- and S-isomers of N-Boc-2-aminopropanol-1. Application of R- and S-isomers of 3-MeSpd for the investigation of the stereospecificity of spermidine transporter and peculiarities of deoxyhypusine synthase reaction are discussed.